Field of the Invention
The present invention relates to the field of gas sensitive materials for gas sensors, and in particular, to a method for preparing a multilayer metal oxide nano-porous thin film gas sensitive material.
Description of Related Art
With rise of the living standards, toxic and harmful gases are everywhere in our lives, and greatly harm the health of the people. Therefore, it is a rather difficult task for researchers to develop a toxic gas sensor of high performance (high sensitivity, high selectivity, and good stability). Metal oxides, as mature gas sensitive materials, are increasingly used by the researchers due to advantages of low cost, stable performance, and capability of performing sensitive detection of low detection limits for various types of gases. The gas sensitive performance of a gas sensitive material is greatly related to the specific surface area of the material. A larger specific surface area of the material leads to more reaction sites in contact with the gas and higher reaction sensitivity to some extent. Therefore, it is a trend of modern researches on the gas sensitive material to make the metal oxide smaller in size to increase its specific surface area, thereby enhancing the response of the gas sensitive material.
The metal oxide porous film material, as a good, gas sensitive material, has higher sensitivity to gas because its specific surface area is larger than that of a bulk film material. In recent years, making the metal oxide film into a porous structure so as to enhance the gas sensitive response of the gas sensitive material is gradually becoming a trend, and also gets more attention from the researchers.
An ordered porous array film material has a high specific surface area as well as a perfect and regular porous array structure, and thus can be well applied in a gas sensitive sensor, such that its application in gas sensors is also becoming a trend. In terms of detection of polluting gases, it is expected and also a challenge to use a metal oxide nano-porous material as a gas sensitive material to improve the selectivity, repeatability and stability of gas sensors. However, the above perfect strategy requires that a perfect nano-porous structure material is synthesized first, and thus the synthesis of the nano-porous material has become a critical factor for wide application of the nano-porous material in high-efficiency gas sensitive devices. At present, some metal oxide porous materials have been prepared by a hydrothermal method, a template preparation method and so on, and a metal oxide porous material, a metal-doped metal oxide porous material, and a mixed metal oxide porous material have also been reported successively. According to the mutual enhancement theory of multiple types of gas sensitive materials, the mutual assisting effect of two different types of metal oxides enables that the gas sensitive response of a combination of two different types of metal oxide gas sensitive materials is higher than the gas sensitive response of a single gas sensitive material, and the gas sensitive parameters are improved. Therefore, the preparation of a multilayer porous film of two or more different types of materials has gradually become a focus in the research on the gas sensitive material, and has a great application prospect in the field of gas sensitive sensors in the future.